The term “pump” is used herein to refer to a device comprising a stator chamber or housing and a rotor that rotates within the chamber to cause sequential intake, compression, and exhaust of a fluid medium such as a gas, a liquid, or a combination thereof. The term, therefore, comprehends not only devices that cause fluid movement but also devices that compress or pressurize fluids with or without ignition and combustion. Further, the term “pump” embraces a reverse operation in which fluid drives a rotor rather than the rotor driving the fluid; i.e., in reverse operation every pump is effectively a motor.
One example of a rotary pump is the well-known Wankel engine that uses an ellipsoid stator chamber and a triangular rotor with seals at the corners.
Another example of a rotary pump is shown in U.S. Pat. No. 4,507,067 to Hansen. The pump in the Hansen patent comprises an elliptical, non-expanding rotor within an elliptical chamber with co-located geometric and rotational centers. The device is characterized by complexity in the number of radially sliding seals required.